Fixes the annual C budget in ELM

The C-states for all budgets (daily/monthly/annual/instantaneous/all time) are
updated when the timestep is 1.

Fixes #6337
[BFB]

components/elm/src/biogeochem/CNPBudgetMod.F90

@@ -546,10 +546,12 @@ subroutine Accum(s_size, budg_fluxN, budg_fluxL, budg_stateL, budg_stateG)
           if (sec_prev == 0 .and. day_prev == 1 .and. month_prev == 1) update_state_beg = .true.
           if (sec_curr == 0 .and. day_curr == 1 .and. month_curr == 1) update_state_end = .true.
        case (p_inf)
-          if (get_nstep() == 1) update_state_beg = .true.
           update_state_end = .true.
        end select
 
+       ! If this is the first time step, update the states for all budget types
+       if (get_nstep() == 1) update_state_beg = .true.
+
        if (update_state_beg) then
           do is = 1, s_size/2 - 1
              budg_stateL(is,ip) = budg_stateL(is, p_inst)